As an Internet Protocol (IP) based network architecture proposed by the 3rd Generation Partnership Project (3GPP), the IP Multimedia Core Network Subsystem (IMS) establishes an open and flexible service environment, supports multimedia applications, and provides rich multimedia services for the users. A PES is an IP based network architecture for accessing traditional terminals to an IMS network is proposed by Telecommunications and Internet Converged Services and Protocols for Advanced Networking (TISPAN).
In the prior art, currently, there have been communication transfer services for session initial protocol (SIP) terminals implemented in the IMS architecture, including blind communication transfer and inquiry communication transfer; some manufacturers utilize this technology to perform blind communication transfer and inquiry communication transfer for traditional H248 terminals in the AGCF, in order to attempt to replace the communication transfer service for the traditional H248 terminals with the above two services. However, the problems with the prior art lie in that: both services of blind communication transfer and inquiry communication transfer have to be registered for a user; a user has to select using blind communication transfer or inquiry communication transfer before a communication transfer is performed, and the selection is unchangeable once being made; user experiences are also different, for example, a service user will not hear a ring-back tone after initiating a communication transfer; and for blind communication transfer and inquiry communication transfer services for existing AGCF users, tight coupling has not been implemented yet.
ETSI 183 043 has been proposed to solve the above problems; however, the existing ETSI 183 043 just describes two implementation modes, i.e., loose coupling and tight coupling, for traditional services for H248 users, such as services of three-party calling and call waiting, and the appendix of ETSI 183 043 also describes related flows. Currently, there is no specification regarding how to perform the communication transfer service for a user belonging to the AGCF, nor any description of related technologies.